Project Summary A detailed census of the structure and role of cell type specific data in the brain is recognized as one of the most promising avenues for advancing our understanding of the human brain in health and disease. The primary goal of this project is to build a foundational community resource for housing single-cell centered data content in the brain. By adopting a three-tiered data, tools, and knowledge paradigm we will lead, together with data generation partners, in the development and deployment of fundamental data models, common community standards, and scientific results to improve our understanding of the diverse cell types in the mammalian brain and its three dimensional organizational logic. This project proposes a unified solution to the development of its resource beginning with a data collection, quantification, and mapping framework for managing data and information across diverse repositories. The first step is to support the acquisition of fundamental data types from data partners by developing the data models and framework for importing structured data into the BRAIN Cell Data Center (BCDC) in consistent data description standards that describe and facilitate best practices for community use of multi-modal single cell data and its content. Toward achieving this end, we will partner with the Neuroscience Information Framework (NIF), International Neuroinformatics Coordinating Facility (INCF), Neuroscience without Borders (NWB), and other standards promoting organizations to leverage and extend existing standards to allow external data contributors to utilize the BCDC. For these data to be coherent, spatial common coordinate frameworks for mapping are essential, and the project develops and extends Allen Institute Mouse Common Coordinate Framework to enable external mapping of key single cell modalities in a 2D and 3D anatomic context for access and visualization at cell, nuclei, and/or population level. The entire resulting data, tools, and knowledge will be made publicly available in a unified and integrated web-accessible Cell Registry and Portal supporting data retrieval, search, visualization, and analysis of cell specific data and knowledge synthesis. The BCDC front end will provide data feature summaries, tools, and resulting knowledge, and links to raw data and high-resolution images, together with a programmable API/SDK that allows the community to build their own analysis applications and contribute tools. Finally, we will amplify public impact through strong BICCN partnership management, communication, standards committees, and analysis working groups, and develop infrastructure for maximizing community usage, publishing standards and tutorials, and coordinating education and outreach.